get diff array php

<?php
$array1 = array("a" => "green", "red", "blue", "red");
$array2 = array("b" => "green", "yellow", "red");
$result = array_diff($array1, $array2);
?>

Array
(
    [1] => blue
)

$a=[1,2,3];
$b=[2,4,6];
$x = array_diff($b,$a);
echo "<pre>";
print_r($x);

<?php
$array1 = array("a" => "green", "red", "blue", "red");
$array2 = array("b" => "green", "yellow", "red");
$result = array_diff($array1, $array2);

print_r($result);
?>